Until recently, polyhydroxystyrenes or derivatives thereof in which the hydroxyl groups are protected with an acid dissociable, dissolution inhibiting group, which display high transparency relative to a KrF excimer laser (248 nm), have been used as the base resin component of chemically amplified resists.
However, these days, the miniaturization of semiconductor elements has progressed even further, and the development of processes using ArF excimer lasers (193 nm) is being vigorously pursued.
For processes using an ArF excimer laser as the light source, resins comprising a benzene ring such as the polyhydroxystyrenes described above have insufficient transparency relative to the ArF excimer laser (193 nm).
Consequently, resins capable of resolving this problem, containing no benzene rings, and comprising a structural unit derived from a (meth)acrylate ester incorporating a polycyclic hydrocarbon ring such as an adamantane ring within the principal chain are attracting considerable interest, and many materials have already been proposed (Japanese Patent (Granted) Publication No. 2881969, Japanese Unexamined Patent Application, First Publication No. Hei 5-346668, Japanese Unexamined Patent Application, First Publication No. Hei 7-234511, Japanese Unexamined Patent Application, First Publication No. Hei 9-73173, Japanese Unexamined Patent Application, First Publication No. Hei 9-90637, Japanese Unexamined Patent Application, First Publication No. Hei 10-161313, Japanese Unexamined Patent Application, First Publication No. Hei 10-319595 and Japanese Unexamined Patent Application, First Publication No. Hei 11-12326).
However, with the development of different etching films in recent years, a variety of etching gases can now be used, and as a result, a new problem has arisen in that surface roughness appears on the resist film following etching.
This surface roughness is different from one which conventional dry etching resistance meet, and in a film etched using a resist pattern as a mask, appears as distortions around the hole patterns in a contact hole pattern, or as line edge roughness in a line and space pattern. Line edge roughness refers to non-uniform irregularities in the line side walls.
Furthermore, in addition to the surface roughness described above, line edge roughness also occurs in the resist pattern following developing.
This line edge roughness also appears as distortions around the hole patterns in a contact hole pattern or as non-uniform irregularities in the line side walls in a line and space pattern.
In addition, the design rules required in modern semiconductor element production continue to become more stringent, and a resolution of no more than 150 nm, and in the vicinity of 100 nm is now required. As a result, further improvements in resolution are needed.
Furthermore, in addition to this improvement in resolution, widening of the depth of focus range characteristics is also desirable.
However, with conventional resist compositions, resolving the above problems has been unsatisfactory, and further improvements have been keenly sought.